This invention relates to gas metal arc welding, flux cored arc welding, and composite cored arc welding, and in particular to a shielding gas composition for use in these processes.
It is well known in the welding art that in shielded metal arc welding, gas metal arc welding, flux cored arc welding, and composite cored arc welding, the shielding gas can affect the process and the quality of the resulting weld.
In these processes it has been common practice to employ a shielding gas which has as its main ingredient argon, an inert gas. Blended into the argon are various mixtures of other gases selected from the group consisting of oxygen, carbon dioxide, and helium. A detailed explanation of shielding gases can be found in publication ANSI/AWS C5.10-94 published by the American Welding Society under the title "Recommended Practices For Shielding Gases For Welding And Plasma Arc Cutting".
The underlying welding processes, in particular gas metal arc welding (GMAW) and flux cored arc welding (FCAW) are explained in detail in volume 2 of the eighth edition of the welding hand book, chapters 4 and 5 respectively, published by the American Welding Society.
According to the Welding Handbook various shielding gas mixtures having been employed in the welding processes that basically combine transfer of metal from a consumable electrode, be it a stick electrode or continuous wire, to a weld pool to create a joint between prepared base metals to be joined.
The gas metal arc welding (GMAW) process is an arc welding process that uses an arc struck between a continuous filler metal electrode and the weld pool. The process is used with shielding supplied by a gas mixture without the application of pressure. The shielding gas mixtures are basically argon with one or more addatives such as oxygen, carbon dioxide, helium or hydrogen.
The flux cored arc welding (FCAW) process involves an arc between a continuous filler metal electrode and the weld pool. The process is used with shielding from a flux contained within the tubular electrode, with or without additional shielding from an externally supplied gas, and without the application of pressure. In the case of flux cored arc welding using external shielding gases, the shielding gases are basically argon with one or more components selected from the group consisting of helium, oxygen and carbon dioxide.
Composite cored arc welding(CCAW) is used to describe an arc welding process where a tublar wire having a center filled with metal powder is used as the electrode material. This process also relies on the use of shielding gases to protect the arc and weld pool.
The various industrial gas suppliers and welding supply manufacturers offer numerous shielding gas mixtures.
In particular Air Products and Chemicals, Inc. has marketed a gas mixture called Astec HP for high deposition of metal and high arc travel speed in the gas metal arc welding process in the flat or horizontal position. The composition offered by this company contains 65% argon 25% helium and 10% carbon dioxide. This particular shielding gas mixture makes it difficult to control the molten metal while welding in positions other than the flat or horizontal position. Furthermore, fine short circuit arc transfer is not easily effected with this mixture.